Preparation method of cubic microcrystalline copper powder, cubic microcrystalline copper powder and application thereof

Abstract

The present invention provides a preparation method of cubic microcrystalline copper powder, cubic microcrystalline copper powder and its application, and specifically relates to the technical field of functional powder preparation. The preparation method of the present invention is to add a first copper salt solution to a reducing agent solution at a rate of 2 to 5 L / min to perform a first reduction reaction to obtain a mixed solution; continue to add a second copper salt solution to the mixed solution at a rate of 0.2 to 1 L / min to perform a second reduction reaction, and finally separate the solid and liquid, wash and dry to obtain the cubic microcrystalline copper powder; wherein the reducing agent solution includes a reducing agent, a template and water. The preparation method provided by the present invention has a simple process, adopts a distribution process of a copper salt solution, effectively controls the growth trend of particles, and obtains cubic microcrystalline copper powder with good dispersibility and uniform particle size distribution.

Description

Technical Field

[0001] The invention relates to the technical field of functional powder preparation, and in particular to a preparation method of cubic microcrystalline copper powder, the cubic microcrystalline copper powder and applications thereof. Background Art

[0002] Copper powder, as a functional basic powder material with high-tech content and high added value, is a hot product that is developing rapidly in the field of materials. It inherits the excellent properties of metallic copper, such as electrical conductivity, thermal conductivity, corrosion resistance and surface finish, and as a functional powder material, copper powder is widely used in emerging fields such as powder metallurgy, friction materials, oil-containing bearings, electrical contact materials, conductive materials, diamond products, mechanical parts, petroleum catalysts, lubricants, conductive and decorative coatings, and electromagnetic shielding materials.

[0003] Among the various copper powder forms, spherical and flake copper powders are widely used in the market. However, cubic copper powder is of particular importance in the preparation of new composite catalysts. It provides a flat substrate that facilitates the attachment of other materials, thereby producing composite catalysts with excellent performance. The flat surface of cubic copper powder is conducive to observing the attachment, and its high dispersibility allows it to be evenly dispersed in organic carriers for the preparation of low-viscosity conductive copper slurries, thereby improving the mechanical and electrical properties of the product.

[0004] There are various methods for preparing copper powder, mainly including physical method and chemical method. Physical methods include physical vapor deposition, high-energy ball milling and gamma ray method, while chemical methods include chemical vapor deposition, chemical precipitation, sol-gel method, hydrothermal method, electrolysis method and liquid phase reduction method. The liquid phase reduction method has obvious advantages in particle morphology control, and the size and morphology of the powder can be flexibly controlled by adjusting the preparation conditions. Although the existing liquid phase reduction method can be used to prepare cubic copper powder, this method has problems such as high heating temperature, high energy consumption, cumbersome operation steps, uneven powder particle size, difficult dispersion and low yield. Therefore, developing a more practical method to prepare cubic microcrystalline copper powder with uniform particle size and easy dispersion is an important direction of current research.

[0005] In view of this, the present invention is proposed. Summary of the invention

[0006] One of the objects of the present invention is to provide a method for preparing cubic microcrystalline copper powder to alleviate at least one of the above technical problems.

[0007] A second object of the present invention is to provide a cubic microcrystalline copper powder.

[0008] A third object of the present invention is to provide an application of cubic microcrystalline copper powder.

[0009] In order to achieve the above-mentioned purpose of the present invention, the following technical solutions are particularly adopted:

[0010] The first aspect of the present invention provides a method for preparing cubic microcrystalline copper powder: adding a first copper salt solution to a reducing agent solution at a rate of 2 to 5 L / min to perform a first reduction reaction to obtain a mixed solution; continuing to add a second copper salt solution to the mixed solution at a rate of 0.2 to 1 L / min to perform a second reduction reaction, and finally solid-liquid separation, washing and drying to obtain the cubic microcrystalline copper powder;

[0011] Wherein, the reducing agent solution comprises a reducing agent, a template agent and water;

[0012] The structural formula of the template is shown in Formula I below:

[0013]

[0014] n is any integer.

[0015] Furthermore, the molecular weight of the template is 10,000-20,000.

[0016] Preferably, the molar ratio of the copper salt to the reducing agent is 3:3-5.

[0017] The molar amount of the copper salt is the total molar amount of the copper salts in the first copper salt solution and the second copper salt solution.

[0018] Furthermore, the reducing agent includes at least one of formaldehyde, ascorbic acid, hydrazine hydrate, sodium borohydride, potassium borohydride, sodium hypophosphite and polyol, preferably ascorbic acid.

[0019] Preferably, in the reducing agent solution, the concentration of the reducing agent is 5-10 wt.%, and the concentration of the template agent is 0.5-2 wt.%.

[0020] Preferably, the pH of the reducing agent solution is 4-7.

[0021] Furthermore, the first copper salt solution and the second copper salt solution have the same composition.

[0022] Preferably, the copper salt in the first copper salt solution includes at least one of copper chloride, copper acetate, copper sulfate and copper nitrate, preferably copper sulfate.

[0023] Preferably, the concentration of the copper salt in the first copper salt solution is 0.4-1.0 mol / L.

[0024] Preferably, the volume ratio of the first copper salt solution to the second copper salt solution is 1:0.1-1.

[0025] Furthermore, the temperature of the first reduction reaction is 60-90° C., and the time is 10-30 min.

[0026] Preferably, the temperature of the second reduction reaction is 60-90° C., and the time is 1-2 hours.

[0027] Furthermore, the solid-liquid separation method includes centrifugation or filtration.

[0028] Furthermore, the drying method is vacuum drying.

[0029] The second aspect of the present invention provides a cubic microcrystalline copper powder prepared by the preparation method described in the first aspect.

[0030] Furthermore, the side length of the cube is 0.6-3 μm.

[0031] The third aspect of the present invention provides the use of the cubic microcrystalline copper powder in preparing a composite catalyst matrix or a conductive copper slurry.

[0032] Compared with the prior art, the present invention has at least the following beneficial effects:

[0033] The preparation method of cubic microcrystalline copper powder provided by the present invention is that the reduction reaction is carried out in two stages. In the first stage, the first copper salt solution is quickly added to quickly reduce copper ions to copper atoms, thereby reaching a saturated atomic concentration, and agglomerating into cubic crystal nuclei under the action of a template agent; in the second stage, the second copper salt solution is slowly added, and the copper ions are slowly reduced. The copper atoms in the solution are lower than the saturated concentration, and no longer nucleate secondary nuclei, and tend to gradually grow on the cubic crystal nuclei obtained by the one-step reduction reaction, and finally reach micron-level cubic copper powder. Among them, the template agent changes the relative growth rate of each crystal face, improves the crystallization habit of the particles, reduces the crystal interface energy, and changes the crystal morphology, thereby preparing cubic microcrystalline copper powder. The preparation method has a simple process, adopts a distribution process of a copper salt solution, effectively controls the growth trend of the particles, and obtains a cubic microcrystalline copper powder with good dispersibility and uniform particle size distribution.

[0034] The cubic microcrystalline copper powder provided by the present invention has good dispersibility and uniform particle size distribution. The side length of the cube is distributed between 0.6 and 3 μm. Compared with spherical copper powder or flaky copper powder with the same particle size, it has higher tap density and lower specific surface area, can meet the needs of high-performance applications, and provides an efficient and reliable material selection for related industrial fields.

[0035] The cubic microcrystalline copper powder provided by the present invention provides better functional powder for preparing a composite catalyst matrix or a conductive copper paste, which is beneficial to improving the performance of the composite catalyst and controlling the morphology of the composite catalyst; the cubic microcrystalline copper powder can be used in the copper conductive paste to prepare a low-viscosity paste under the same square resistance requirement, thereby improving the conductivity and printability of the copper conductive paste. BRIEF DESCRIPTION OF THE DRAWINGS

[0036] In order to more clearly illustrate the specific implementation methods of the present invention or the technical solutions in the prior art, the drawings required for use in the specific implementation methods or the description of the prior art will be briefly introduced below. Obviously, the drawings described below are some implementation methods of the present invention. For ordinary technicians in this field, other drawings can be obtained based on these drawings without paying creative work.

[0037] Figure 1 is a scanning electron microscope image of the cubic microcrystalline copper powder of Example 1;

[0038] Figure 2 is a scanning electron microscope image of the cubic microcrystalline copper powder of Example 2;

[0039] Figure 3 is a scanning electron microscope image of the cubic microcrystalline copper powder of Example 3;

[0040] Figure 4 is a scanning electron microscope image of the cubic microcrystalline copper powder of Example 4;

[0041] Figure 5 is a scanning electron microscope image of the cubic microcrystalline copper powder of Example 5;

[0042] Figure 6 is a scanning electron microscope image of the cubic microcrystalline copper powder of Example 6;

[0043] Figure 7 is a scanning electron microscope image of the cubic microcrystalline copper powder of Example 7;

[0044] Figure 8 is a scanning electron microscope image of the cubic microcrystalline copper powder of Example 8;

[0045] Fig. 9 is a scanning electron microscope image of the cubic microcrystalline copper powder of Example 9;

[0046] Fig.10 is a scanning electron microscope image of the cubic microcrystalline copper powder of Comparative Example 1;

[0047] Fig.11 This is a scanning electron microscope image of the cubic microcrystalline copper powder of Comparative Example 2;

[0048] Fig.12 This is a scanning electron microscope image of the cubic microcrystalline copper powder of Comparative Example 3. DETAILED DESCRIPTION

[0049] The embodiments of the present invention will be described in detail below in conjunction with the embodiments and examples, but those skilled in the art will understand that the following embodiments and examples are only used to illustrate the present invention and should not be considered to limit the scope of the present invention. Based on the embodiments in the present invention, all other embodiments obtained by ordinary technicians in this field without making creative work are within the scope of protection of the present invention.

[0050] The first aspect of the present invention provides a method for preparing cubic microcrystalline copper powder: adding a first copper salt solution to a reducing agent solution at a rate of 2 to 5 L / min to perform a first reduction reaction to obtain a mixed solution; continuing to add a second copper salt solution to the mixed solution at a rate of 0.2 to 1 L / min to perform a second reduction reaction, and finally solid-liquid separation, washing and drying to obtain the cubic microcrystalline copper powder;

[0051] Wherein, the reducing agent solution comprises a reducing agent, a template agent and water;

[0052] The structural formula of the template is shown in Formula I below:

[0053]

[0054] n is any integer.

[0055] The preparation method of cubic microcrystalline copper powder provided by the present invention is that the reduction reaction is carried out in two stages. In the first stage, the first copper salt solution is quickly added to quickly reduce copper ions to copper atoms, thereby reaching a saturated atomic concentration, and agglomerating into cubic crystal nuclei under the action of a template agent; in the second stage, the second copper salt solution is slowly added, and the copper ions are slowly reduced. The copper atoms in the solution are lower than the saturated concentration, and no longer nucleate secondary nuclei, and tend to gradually grow on the cubic crystal nuclei obtained by the one-step reduction reaction, and finally reach micron-level cubic copper powder. Among them, the template agent changes the relative growth rate of each crystal face, improves the crystallization habit of the particles, reduces the crystal interface energy, and changes the crystal morphology, thereby preparing cubic microcrystalline copper powder. The preparation method has a simple process, adopts a distribution process of a copper salt solution, effectively controls the growth trend of the particles, and obtains a cubic microcrystalline copper powder with good dispersibility and uniform particle size distribution.

[0056] Typically but not limiting, the addition rate of the first copper salt solution can be, for example, 2 L / min, 2.5 L / min, 3 L / min, 3.5 L / min, 4 L / min or 5 L / min, or any value in the range of 2 to 5 L / min; the addition rate of the second copper salt solution can be, for example, 0.2 L / min, 0.3 L / min, 0.4 L / min, 0.5 L / min, 0.6 L / min, 0.7 L / min, 0.8 L / min or 1 L / min, or any value in the range of 0.2 to 1 L / min.

[0057] In one embodiment of the present invention, the template is a homemade product, and the preparation method is as follows:

[0058] Dissolve 4-vinylpyridine, hydroxyethyl acrylate, maleic anhydride and initiator ammonium persulfate in 90% ethanol aqueous solution to obtain a reaction solution. Take 1 / 2 of the reaction solution and heat it to 70°C, then slowly add the remaining reaction solution and keep it at 70°C for 7 hours. Finally, lower the temperature to room temperature to terminate the reaction, precipitate the product with acetone and wash it 3 to 5 times, and dry the filtered product at 50°C to constant weight to obtain a light yellow powder as the template.

[0059] The template agent, through its unique steric hindrance structure, directionally adsorbs the copper crystal nucleus at the anchor end, and the mutual repulsion of the bifunctional solvation chains prevents the crystal nuclei from agglomerating and combining, and finally gradually grows from the original crystal nucleus surface into a cubic structure crystal.

[0060] Furthermore, the molecular weight of the template is 10,000-20,000.

[0061] Typically but not limiting, the molecular weight of the template may be, for example, 10,000, 12,000, 14,000, 16,000, 18,000, 20,000, or any value within the range of 10,000 to 20,000.

[0062] Preferably, the molar ratio of the copper salt to the reducing agent is 3:3-5.

[0063] The molar amount of the copper salt is the total molar amount of the copper salts in the first copper salt solution and the second copper salt solution.

[0064] Typically but not limiting, the molar ratio of the copper salt to the reducing agent may be 3:3, 3:4, 3:5, or any ratio within the range of 3:3 to 5.

[0065] Furthermore, the reducing agent includes at least one of formaldehyde, ascorbic acid, hydrazine hydrate, sodium borohydride, potassium borohydride, sodium hypophosphite and polyol, preferably ascorbic acid.

[0066] Preferably, in the reducing agent solution, the concentration of the reducing agent is 5-10 wt.%, and the concentration of the template agent is 0.5-2 wt.%.

[0067] Typically but not limiting, in the reducing agent solution, the concentration of the reducing agent can be, for example, 5wt.%, 6wt.%, 7wt.%, 8wt.%, 9wt.% or 10wt.%, or any value in the range of 5wt.% to 10wt.%; the concentration of the template can be, for example, 0.5wt.%, 0.75wt.%, 1wt.%, 1.25wt.%, 1.5wt.%, 1.75wt.% or 2wt.%, or any value in the range of 0.5wt.% to 2wt.%.

[0068] Preferably, the pH of the reducing agent solution is 4-7.

[0069] Controlling the pH of the reducing agent solution within the range of 4 to 7 is to ensure that copper ions are converted into copper atoms to the maximum extent possible while preventing copper ions from forming precipitation with hydroxide or other anions. In this pH range, the process of reducing copper ions to copper atoms is more effective, because too high a pH value may cause copper ions to react with hydroxide ions to form water-insoluble copper hydroxide precipitation, which will reduce the yield of copper powder and affect its physical properties. On the contrary, too low a pH value may increase the risk of other competitive reactions in the solution, such as the formation of complexes between copper ions and chloride ions, which is also not conducive to the formation of copper powder.

[0070] In the specific operation process, an acid-base regulator needs to be added to the reducing agent solution to adjust the pH of the reducing agent solution to 4-7. The acid-base regulator includes sodium hydroxide or sodium carbonate.

[0071] Typically but not limiting, the pH value of the reducing agent solution may be, for example, 4.0, 4.5, 5.0, 5.5, 6.0, 6.5, 7.0, or any value within the range of 4-7.

[0072] Preferably, the copper salt in the first copper salt solution includes at least one of copper chloride, copper acetate, copper sulfate and copper nitrate, preferably copper sulfate.

[0073] Preferably, the concentration of the copper salt in the first copper salt solution is 0.4-1.0 mol / L.

[0074] Typically but not limitatively, the concentration of the copper salt in the first copper salt solution can be, for example, 0.4 mol / L, 0.5 mol / L, 0.6 mol / L, 0.7 mol / L, 0.8 mol / L, 0.9 mol / L or 1 mol / L, or any value within the range of 0.4 to 1 mol / L.

[0075] Preferably, the volume ratio of the first copper salt solution to the second copper salt solution is 1:0.1-1.

[0076] The size of the cubic microcrystalline copper powder is related to the volume ratio of the first copper salt solution and the second copper salt solution. The more copper salt solution is added quickly in the first reduction reaction, the higher the copper ion concentration in the system, the more nuclei are formed, so that there are fewer copper ions for growth later, and the final cubic microcrystalline copper powder has a smaller particle size; on the contrary, the less copper salt solution is added quickly in the first reduction reaction, and a certain number of nuclei is reached, so that more copper salt solution is reserved for growth, thereby achieving the purpose of controlling the particle size. In order to avoid secondary nucleation in the second reduction reaction, the volume ratio of the first copper salt solution to the second copper salt solution must be greater than or equal to 1:1.

[0077] Typically but not limitatively, the volume ratio of the first copper salt solution to the second copper salt solution can be 1:0.1, 1:0.2, 1:0.3, 1:0.4, 1:0.5, 1:0.6, 1:0.7, 1:0.8 or 1:0.9, or any value within the range of 1:0.1 to 1.

[0078] Furthermore, the temperature of the first reduction reaction is 60-90° C., and the time is 10-30 min.

[0079] Typically but not limiting, the temperature of the first reduction reaction can be, for example, 60°C, 65°C, 70°C, 75°C, 80°C, 85°C or 90°C, or any value within the range of 60 to 90°C; the time is 10 min, 12 min, 15 min, 20 min, 25 min or 30 min, or any value within the range of 10 to 30 min.

[0080] Preferably, the temperature of the second reduction reaction is 60-90° C., and the time is 1-2 hours.

[0081] Typically but not limiting, the temperature of the second reduction reaction can also be 60°C, 65°C, 70°C, 75°C, 80°C, 85°C or 90°C, or any value within the range of 60 to 90°C; the time is 1h, 1.5h or 2h, or any value within the range of 1 to 2h.

[0082] In the specific process of preparing cubic microcrystalline copper powder, although the first reduction reaction and the second reduction reaction limit the reaction temperature, in order to react more efficiently, the first copper salt solution and the second copper salt solution can be heated to 50-80°C in advance. The purpose of this is to ensure that the solution has reached a suitable reaction temperature before adding the reducing agent solution, so that the reaction is more rapid and complete. Preheating the solution can reduce the energy demand in the initial stage of the reaction, accelerate the reaction kinetics, and help the directional growth of copper ions into a cubic form during the reduction process.

[0083] In addition, the preheating step also helps to reduce the temperature fluctuation of the reaction system, thereby providing a more uniform and stable growth environment, which is crucial for controlling the crystal morphology and size distribution of the copper powder. Within the appropriate temperature range, the viscosity and molecular mobility of the copper salt solution are also optimized, which helps to form uniform copper powder particles during the reduction process and reduce the occurrence of agglomeration.

[0084] Furthermore, the solid-liquid separation method includes centrifugation or filtration.

[0085] Furthermore, the drying method is vacuum drying.

[0086] The second aspect of the present invention provides a cubic microcrystalline copper powder prepared by the preparation method described in the first aspect.

[0087] The cubic microcrystalline copper powder provided by the present invention has good dispersibility and uniform particle size distribution. The side length of the cube is distributed between 0.6 and 3 μm. Compared with spherical copper powder or flaky copper powder with the same particle size, it has higher tap density and lower specific surface area, can meet the needs of high-performance applications, and provides an efficient and reliable material selection for related industrial fields.

[0088] Furthermore, the side length of the cube is 0.6-3 μm.

[0089] The third aspect of the present invention provides the use of the cubic microcrystalline copper powder in preparing a composite catalyst matrix or a conductive copper slurry.

[0090] The cubic microcrystalline copper powder provided by the present invention provides better functional powder for preparing a composite catalyst matrix or a conductive copper paste, which is beneficial to improving the performance of the composite catalyst and controlling the morphology of the composite catalyst; the cubic microcrystalline copper powder can be used in the copper conductive paste to prepare a low-viscosity paste under the same square resistance requirement, thereby improving the conductivity and printability of the copper conductive paste.

[0091] The present invention is further described below by specific examples and comparative examples, but it should be understood that these examples are only used for more detailed description and should not be understood as limiting the present invention in any form. The raw materials used in the examples and comparative examples of the present invention, if no specific conditions are specified, are carried out according to conventional conditions or conditions recommended by the manufacturer. The reagents or instruments used without indicating the manufacturer are all conventional products that can be purchased commercially.

[0092] The preparation methods of the templates of the following examples and comparative examples are as follows:

[0093] Dissolve 4-vinylpyridine, hydroxyethyl acrylate, maleic anhydride and initiator ammonium persulfate in 90% ethanol aqueous solution to obtain a reaction solution. Take 1 / 2 of the reaction solution and heat it to 70°C, then slowly add the remaining reaction solution and keep it at 70°C for 7 hours. Finally, lower the temperature to room temperature to terminate the reaction, precipitate the product with acetone and wash it 3 to 5 times, and dry the filtered product at 50°C to constant weight to obtain a light yellow powder as the template.

[0094] Example 1

[0095] This embodiment provides a cubic microcrystalline copper powder, and the preparation method is as follows:

[0096] 1. Dissolve 87.5 g of copper sulfate pentahydrate in 0.5 L of deionized water, stir evenly with magnetic force to prepare a 0.7 mol / L copper sulfate solution, and divide the solution into two parts with a volume ratio of 1:1 to obtain a first copper sulfate solution and a second copper sulfate solution.

[0097] 2. Weigh 82.2g of ascorbic acid and 15g of template agent and add them into 1L of water. After stirring to dissolve, add 4mol / L sodium hydroxide solution to the solution, adjust the pH of the solution to 5.0, obtain a reducing agent solution, and heat it to 80°C.

[0098] 3. Heat the first copper sulfate solution to 70°C, add it to the reducing agent solution at a rate of 3L / min, and react at 80°C for 20min to obtain a mixed solution. Then heat the second copper sulfate solution to 70°C, add it to the mixed solution at a rate of 0.5L / min, and react at 80°C for 2h. After the reaction, a cubic microcrystalline copper powder dispersion is obtained.

[0099] 4. Centrifuge the cubic microcrystalline copper powder dispersion, wash the precipitate, and vacuum dry it to obtain the cubic microcrystalline copper powder.

[0100] Example 2

[0101] This embodiment provides a cubic microcrystalline copper powder. The difference from Embodiment 1 is that the volume ratio of the first copper sulfate solution to the second copper sulfate solution is 2:1. The remaining raw materials and preparation methods are the same as those in Embodiment 1 and are not described again.

[0102] Example 3

[0103] This embodiment provides a cubic microcrystalline copper powder. The difference from Embodiment 1 is that the volume ratio of the first copper sulfate solution to the second copper sulfate solution is 10:1. The remaining raw materials and preparation methods are the same as those in Embodiment 1 and are not described again.

[0104] Example 4

[0105] This embodiment provides a cubic microcrystalline copper powder, and the preparation method is as follows:

[0106] 1. Dissolve 50 g of copper sulfate pentahydrate in 0.5 L of deionized water, stir evenly with a magnetic stirrer to prepare a 0.4 mol / L copper sulfate solution. Divide the solution into two parts with a volume ratio of 10:1 to obtain a first copper sulfate solution and a second copper sulfate solution.

[0107] Steps 2-4 are the same as Steps 2-4 in Example 3.

[0108] Example 5

[0109] This embodiment provides a cubic microcrystalline copper powder, and the preparation method is as follows:

[0110] 1. Dissolve 125 g of copper sulfate pentahydrate in 0.5 L of deionized water, stir evenly with a magnetic stirrer to prepare a 1.0 mol / L copper sulfate solution. Divide the solution into two parts with a volume ratio of 10:1 to obtain a first copper sulfate solution and a second copper sulfate solution.

[0111] Steps 2-4 are the same as Steps 2-4 in Example 3.

[0112] Example 6

[0113] This embodiment provides a cubic microcrystalline copper powder. The difference from Embodiment 3 is that the amount of template added is 5.44 g, and the other raw materials and preparation method are the same as those in Embodiment 3, which will not be described again.

[0114] Example 7

[0115] This embodiment provides a cubic microcrystalline copper powder. The difference from Embodiment 3 is that the amount of template added is 22.1 g, and the other raw materials and preparation method are the same as those in Embodiment 3, which will not be described again.

[0116] Example 8

[0117] This embodiment provides a cubic microcrystalline copper powder. The difference from Example 3 is that the addition rate of the first copper sulfate solution is 2 L / min, and the addition rate of the second copper sulfate solution is 1 L / min. The remaining raw materials and preparation methods are the same as those in Example 3 and are not repeated here.

[0118] Example 9

[0119] This embodiment provides a cubic microcrystalline copper powder. The difference from Example 3 is that the addition rate of the first copper sulfate solution is 5 L / min, and the addition rate of the second copper sulfate solution is 0.2 L / min. The remaining raw materials and preparation methods are the same as those in Example 3 and are not repeated here.

[0120] Comparative Example 1

[0121] This comparative example provides a cubic microcrystalline copper powder. The difference from Example 1 is that no template is added to the reducing agent solution. The remaining raw materials and preparation method are the same as those in Example 1 and will not be described again.

[0122] Comparative Example 2

[0123] This comparative example provides a cubic microcrystalline copper powder. The difference from Example 3 is that the addition rate of the second copper sulfate solution is 3 L / min, which is the same as the addition rate of the first copper sulfate solution. The remaining raw materials and steps are the same as those in Example 3 and are not repeated here.

[0124] Comparative Example 3

[0125] This comparative example provides a cubic microcrystalline copper powder. The difference from Example 3 is that the addition rate of the first copper sulfate solution is 0.5 L / min, which is the same as the addition rate of the second copper sulfate solution. The remaining raw materials and steps are the same as those in Example 3 and are not repeated here.

[0126] Characterization example

[0127] The cubic microcrystalline copper powder obtained in the embodiment and the comparative example was subjected to scanning electron microscopy, and the obtained SEM images corresponded to the following: Figures 1 to 12 shown.

[0128] from Figure 1 It can be seen that the cubic microcrystalline copper powder prepared by the preparation method of Example 1 has good dispersibility, a corrugated surface, rounded edges and corners, and a cubic shape with a side length of 2 to 3 μm.

[0129] from Figure 2 It can be seen that the cubic microcrystalline copper powder prepared by the preparation method of Example 2 has good dispersibility, a smooth and flat surface, sharp edges and corners, and a cubic shape with a side length of 1 to 2 μm.

[0130] from Figure 3It can be seen that as the proportion of the first copper salt solution increases, rapid and large-scale nucleation occurs in the initial stage, causing the particle size of the copper particles to gradually decrease. The cubic microcrystalline copper powder prepared by the preparation method of Example 3 has good dispersibility, a smooth and flat surface, sharp edges and corners, and a cubic shape with a side length of 0.8 to 1 μm.

[0131] from Figure 4 It can be seen that the cubic microcrystalline copper powder prepared by the preparation method of Example 4 has good dispersibility, a smooth surface, sharp edges and corners, and a cubic shape with a side length of 1 to 2 μm. The concentration of reactants is reduced, the number of nuclei in the early stage is reduced, and the particle size is slightly larger than that of Example 3.

[0132] from Figure 5 It can be seen that the cubic microcrystalline copper obtained by the preparation method of Example 5 has a smooth surface and sharp edges and corners, but the copper particles are adhered to each other, the dispersion is general, and the side length is 0.6-0.8 μm. As the concentration of the reactants increases, a large number of nuclei are formed in the early stage, and the copper crystal nuclei collide with each other and easily adhere together during the growth process.

[0133] from Figure 6 It can be seen that the cubic microcrystalline copper powder prepared by the preparation method of Example 6 has a smooth surface, rounded edges and corners, general dispersibility, and a cubic shape with a side length of 0.8 to 1 μm.

[0134] from Figure 7 It can be seen that the cubic microcrystalline copper powder prepared by the preparation method of Example 7 has good dispersibility, a smooth surface, sharp edges and corners, and a cubic shape with a side length of 1 to 2 μm. The mass proportion of the template agent affects the cubic morphology of the copper particles. With the increase of the template agent, the copper particles gradually change from a spherical shape to a cubic shape.

[0135] from Figure 8 It can be seen that the cubic microcrystalline copper powder prepared by the preparation method of Example 8 has good dispersibility, a smooth and flat surface, sharp edges and corners, and a cubic shape with a side length of 0.8 to 1 μm.

[0136] from Fig. 9 It can be seen that the surface of the cubic microcrystalline copper powder prepared by the preparation method of Example 9 is smooth and flat, with clear edges and corners, but there is adhesion between the copper particles, the dispersibility is general, and the side length is 0.6-0.8 μm. The dripping speed of the first copper salt solution is accelerated, a large amount of nucleation is formed in the early stage, the nucleation rate is dominant relative to the growth rate, and the copper crystal nuclei collide with each other and easily adhere to each other during the growth process, so the cubic microcrystalline particles are small in size and have a small amount of adhesion to each other.

[0137] from Fig.10 It can be seen that without the effect of the template agent, the copper powder obtained in Comparative Example 1 presents an irregular spherical shape, general dispersibility, a particle size of 2 to 3 μm, and no prominent cubic features.

[0138] from Fig.11 It can be seen that the cubic microcrystalline copper powder prepared by the preparation method of Comparative Example 2 has poor dispersibility, is of different sizes, and the copper particles are adhered to each other. Because the same droplet addition speed allows nucleation and growth to occur simultaneously in the system, the particles that nucleate first in the early stage grow preferentially, and the particles that nucleate later have a smaller particle size.

[0139] from Fig.12 It can be seen that the cubic microcrystalline copper powder obtained by the preparation method of Comparative Example 3 has poor dispersibility, is of different sizes, and the copper particles are adhered to each other. As the dropwise addition speed is slower, the reaction is slower. After some copper particles are preferentially nucleated, no more nucleation occurs in the system, and the generation rate dominates, resulting in some copper particles being larger in size and severely adhered.

[0140] Finally, it should be noted that the above embodiments are only used to illustrate the technical solutions of the present invention, rather than to limit it. Although the present invention has been described in detail with reference to the aforementioned embodiments, those skilled in the art should understand that they can still modify the technical solutions described in the aforementioned embodiments, or replace some or all of the technical features therein with equivalents. However, these modifications or replacements do not cause the essence of the corresponding technical solutions to deviate from the scope of the technical solutions of the embodiments of the present invention.

Claims

1. A method for preparing cubic microcrystalline copper powder, characterized in that: Adding the first copper salt solution to the reducing agent solution at a rate of 2-5 L / min to perform a first reduction reaction to obtain a mixed solution; Continue to add the second copper salt solution to the mixed solution at a rate of 0.2-1 L / min to perform a second reduction reaction, and finally separate the solid and liquid, wash and dry to obtain the cubic microcrystalline copper powder; Wherein, the reducing agent solution comprises a reducing agent, a template agent and water; The structural formula of the template is shown in Formula I below: Formula I n is any integer; The molecular weight of the template is 10000-20000; The preparation method of the template agent is as follows: 4-vinylpyridine, hydroxyethyl acrylate, maleic anhydride and initiator ammonium persulfate are dissolved in a 90% ethanol aqueous solution to obtain a reaction solution; 1 / 2 of the reaction solution is heated to 70°C, and then the remaining reaction solution is slowly added dropwise, and the temperature is kept at 70°C for 7 hours; finally, the temperature is lowered to room temperature to terminate the reaction, the product is precipitated with acetone and washed 3 to 5 times, and the filtered product is dried at 50°C to constant weight to obtain a light yellow powder as the template agent.

2. The preparation method according to claim 1, characterized in that: The molar ratio of copper salt to reducing agent is 3:3~5; The molar amount of the copper salt is the total molar amount of the copper salts in the first copper salt solution and the second copper salt solution.

3. The preparation method according to claim 1, characterized in that: The reducing agent includes at least one of formaldehyde, ascorbic acid, hydrazine hydrate, sodium borohydride, potassium borohydride, sodium hypophosphite and polyol.

4. The preparation method according to claim 1, characterized in that: In the reducing agent solution, the concentration of the reducing agent is 5-10 wt.%, and the concentration of the template agent is 0.5-2 wt.%.

5. The preparation method according to claim 1, characterized in that: The pH of the reducing agent solution is 4-7.

6. The preparation method according to any one of claims 1 to 5, characterized in that The first copper salt solution and the second copper salt solution have the same composition.

7. The preparation method according to any one of claims 1 to 5, characterized in that The copper salt in the first copper salt solution includes at least one of copper chloride, copper acetate, copper sulfate and copper nitrate.

8. The preparation method according to any one of claims 1 to 5, characterized in that The concentration of the copper salt in the first copper salt solution is 0.4-1.0 mol / L.

9. The preparation method according to any one of claims 1 to 5, characterized in that The volume ratio of the first copper salt solution to the second copper salt solution is 1:0.1~1.

10. The preparation method according to any one of claims 1 to 5, characterized in that: The temperature of the first reduction reaction is 60-90° C. and the time is 10-30 min.

11. The preparation method according to any one of claims 1 to 5, characterized in that: The temperature of the second reduction reaction is 60-90° C. and the time is 1-2 hours.

12. The preparation method according to any one of claims 1 to 5, characterized in that: The solid-liquid separation method includes centrifugation or filtration.

13. The preparation method according to any one of claims 1 to 5, characterized in that: The drying method is vacuum drying.

14. A cubic microcrystalline copper powder, characterized in that: The method is prepared according to any one of claims 1 to 13.

15. The cubic microcrystalline copper powder according to claim 14, characterized in that: The side length of the cube is 0.6~3μm.

16. Use of the cubic microcrystalline copper powder according to claim 14 or 15 in preparing a composite catalyst matrix or a conductive copper slurry.

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